Knowledge Bank

The main Sch""{u}ler $band1,2$ of the ammonium radical $NH3,4$ has been $assigned3,4$ as the 0-0 band of the transition $3p2F2-3S2A1$. In the vibrational structure of this system, bands near the positions expected for the 1-0 and 0-1 transitions of the bending vibrations $\nu 2(e)$ and $v4(f2)$ have been observed with partially resolved rotational $structure5$. The theory of the rotational structure of these bands, allowing for the doublet splitting and the Jahn-Teller effect in the upper state, will be discussed and compared with observed spectra for the $ND4$ isotope.